Fix issue 84

Author: kosme

Examples/FFT_02/FFT_02.ino

@@ -3,7 +3,7 @@
 	Example of use of the FFT library to compute FFT for several signals over a range of frequencies.
         The exponent is calculated once before the execution since it is a constant.
         This saves resources during the execution of the sketch and reduces the compiled size.
-        The sketch shows the time that the computing is taking.
+        The sketch shows the time that the computation takes.
         Copyright (C) 2014 Enrique Condes
 
 	This program is free software: you can redistribute it and/or modify

library.json

@@ -20,7 +20,7 @@
       "email": "contact@arduinoos.com"
     }
   ],
-  "version": "1.6",
+  "version": "1.6.1",
   "frameworks": ["arduino","mbed","espidf"],
   "platforms": "*",
   "headers": "arduinoFFT.h"

library.properties

@@ -1,5 +1,5 @@
 name=arduinoFFT
-version=1.6
+version=1.6.1
 author=Enrique Condes <enrique@shapeoko.com>
 maintainer=Enrique Condes <enrique@shapeoko.com>
 sentence=A library for implementing floating point Fast Fourier Transform calculations on Arduino.

src/arduinoFFT.cpp

@@ -103,9 +103,10 @@ void arduinoFFT::Compute(FFTDirection dir) {
   }
   // Scaling for reverse transform /
   if (dir != FFT_FORWARD) {
+    double reciprocal = 1.0 / this->_samples;
     for (uint16_t i = 0; i < this->_samples; i++) {
-      this->_vReal[i] /= this->_samples;
-      this->_vImag[i] /= this->_samples;
+      this->_vReal[i] *= reciprocal;
+      this->_vImag[i] *= reciprocal;
     }
   }
 }
@@ -169,9 +170,10 @@ void arduinoFFT::Compute(double *vReal, double *vImag, uint16_t samples,
   }
   // Scaling for reverse transform
   if (dir != FFT_FORWARD) {
+    double reciprocal = 1.0 / samples;
     for (uint16_t i = 0; i < samples; i++) {
-      vReal[i] /= samples;
-      vImag[i] /= samples;
+      vReal[i] *= reciprocal;
+      vImag[i] *= reciprocal;
     }
   }
 }
@@ -535,7 +537,7 @@ uint8_t arduinoFFT::Exponent(uint16_t value) {
 #warning("This method may not be accessible on future revisions.")
   // Calculates the base 2 logarithm of a value
   uint8_t result = 0;
-  while (((value >> result) & 1) != 1)
+  while (value >>= 1)
     result++;
   return (result);
 }